1. Field of the Invention
This invention relates to a character and picture data compression apparatus which collectively compresses document data of the character code form and still picture data and moving picture data of the bit map form of binary or multiple values.
2. Description of the Related Art
Much effort has been and is being directed to development of a portable terminal equipment wherein character data and/or picture data of binary or multiple values of characters, line drawings, photographs and so forth recorded in a book, a newspaper, a magazine or the like are recorded onto an electronic, optical or magnetic recording medium. Thus, allowing the recorded data to be read out and developed into a display image so that it may be displayed on a display apparatus such as a liquid crystal display apparatus, or an equipment wherein a display image developed in such a manner as described above is displayed on a display apparatus such as a CRT (cathode ray tube) apparatus. Meanwhile, as a result of development of multi-media in recent years, recording data often include, in addition to character data and still picture data, moving picture data of binary or multiple values called simplified animation.
FIG. 6 shows a system construction by which a display image in which characters, a still picture and a moving picture are included in a mixed condition which is displayed. Referring to FIG. 6, document data wherein characters and so forth are represented in character codes of 2 bytes are recorded in a character recording apparatus 101, and still picture data and moving picture data of the bit map form are recorded in a still picture recording apparatus 102 and a moving picture recording apparatus 103, respectively. When the data are to be displayed, a display image composition section 104 reads out the document data from the character recording apparatus 101 and passes them on to a data display section 105 so that the document is displayed in a document displaying area of a screen of a display apparatus 106. Simultaneously, the display image composition section 104 reads out the still picture data of the bit map form from the still picture recording apparatus 102 and passes them on to the data display section 105 so that the still picture is displayed in a still picture displaying area of the screen of the display apparatus 106. Further, the display image composition section 104 reads out the moving picture data of the bit map form of the first page from the moving picture recording apparatus 103 and passes them on to the data display section 105 so that the moving picture data are displayed in a moving picture displaying area of the screen of the display apparatus 106. Similarly, the display image composition section 104 successively reads out the moving picture data of the bit map form of the second and succeeding pages at predetermined time intervals and passes them on to the data display section 105 so that the moving picture display area of the screen of the display apparatus 106 is successively updated with the moving picture data.
In the system construction described above, where a recording medium having a comparatively small recording capacity such as a floppy disk is used for any of the recording apparatus 101 to 103, or even if a recording medium having a sufficiently large recording capacity is employed, where a large amount of still picture data or moving picture data is to be stored, care must be taken regarding the shortage of the recording capacity of the recording apparatus.
FIG. 7 shows another system construction which solves the problem just described. Referring to FIG. 7, the system shown includes three decompression sections 107, 108 and 109 in addition to similar components to those of the system described above with reference to FIG. 6. In the present system, document data compressed using a known data compression technique are recorded into the character recording apparatus 101 whereas data of a still picture and a moving picture of the bit map form compressed using a known data compression technique are recorded also into the still picture recording apparatus 102 and the moving picture recording apparatus 103, respectively. Then, when the data are to be displayed, the data are decompressed by the decompression sections 107, 108 and 109 and then passed on via the display image composition section 104 to the data display section 105 so that they are displayed in the individual displaying areas of the screen of the display apparatus 106.
With the construction of the system of FIG. 7, since a document, a still picture and a moving picture are recorded in individually compressed conditions, the capacity required for each recording apparatus is small compared to that of the system of FIG. 6. The data compression techniques for a document, a still picture and a moving picture have exhibited remarkable progresses in recent years, and data compression techniques having a high compression efficiency have been proposed. Thus, use of any of the techniques would allow further reduction in storage capacity.
For example, Japanese Patent Laid-Open Application No. Heisei 2-205982 discloses a technique wherein a nature of a picture of an object of compression is identified based on a statistical distribution of the compression object picture, and an optimum one of a plurality of data compression algorithms prepared in advance is selectively used based on a result of the identification to compress data. This technique can be utilized for compression of still picture data.
Meanwhile, Japanese Patent Laid-Open Application No. Showa 64-10387 discloses another technique wherein a moving picture is represented in difference data between frames and the data are represented in two kinds of binary data to perform compression processing such as run-length compression which is used for compression of ordinary frame data. This technique can be utilized for compression of moving picture data. Further, various methods have been proposed for the compression technique of character codes, such as a method which employs a combination of several coding methods. Those techniques can be utilized for compression of document data. Naturally, also such a high efficiency coding technique as the MPEG or the JPEG can be applied to compression of moving picture data.
In this manner, the approaches to reduction in storage capacity in systems which display a display image in which a still picture and a moving picture are included in a mixed condition have been principally directed to an effort to raise the compression efficiency of document data themselves, a still picture itself or a moving picture itself. Consequently, although the compression efficiency exhibits some improvement, since the document data, still picture and moving picture are compressed independently of each other, another problem is invited that a large scale is required for a compression apparatus used for compression of those data. Particularly, with such a system which selectively uses a plurality of data compression algorithms, as disclosed in Japanese Patent Laid-Open Application No. Heisei 2-205982 mentioned hereinabove, or another system which compresses character codes using a combination of several coding methods, the problem of increase in scale of the compression apparatus is even more significant.